1. Field of the Invention
The present invention relates to a recoil starter in which a rope reel is rotated by pulling a recoil rope wound around the rope reel, the rotation of the rope reel is transmitted via a one-way clutch mechanism such as a centrifugal ratchet mechanism to a rotary member such as a flywheel magnet coupled to a crankshaft of an engine, to rotate the rotary member, whereby the crankshaft is rotated to start the engine.
2. Description of the Related Art
It has been known to employ the following structure in a recoil starter in which a rope reel is rotated by pulling a recoil rope wound around the rope reel, and the rotation of the rope reel is transmitted via a one-way clutch mechanism such as a centrifugal ratchet mechanism to a rotary member such as a flywheel magnet or a driving pulley coupled to a crankshaft of an engine, to rotate the rotary member, whereby the crankshaft is rotated to start the engine. A cam is rotatably placed between the rope reel around which the recoil rope is wound; and the rotary member which is coupled to the crankshaft, and the one-way clutch mechanism is formed between the cam and the rotary member. A damper spring which is wound into a torsion coil spring-like shape is interposed between the rope reel and the cam to elastically couple the rope reel with the cam, so that the rotation of the rope reel is transmitted to the cam via the damper spring, whereby a shock which is caused by load variation during engine start, and which is transmitted to the hand is absorbed. Moreover, the rotational force of the rope reel is accumulated in the damper spring, and the crankshaft is rotated at a high speed by the accumulated rotational force.
A conventional recoil starter is configured in the following manner (for example, see JP-UM-A-2-149872). A rope reel around which a recoil rope is wound, and a cam which forms a clutch mechanism with respect to a driving pulley coupled to a crankshaft of an engine are rotatably supported by a support shaft formed in a case. Bosses having the same outer diameter are formed on the outer peripheral faces of the rope reel and the cam, respectively. A damper spring which is formed into a torsion coil spring-like shape is mounted on the outer peripheries of the bosses. The both ends of the damper respectively, so that the rope reel and the cam are coupled with each other in the rotation direction via the damper spring. When the recoil rope is pulled, the rope reel is rotated. The rotation of the rope reel is transmitted to the cam via the damper spring. The cam is blocked from rotating by the starting resistance of the engine, and the damper spring is twisted to buffer a shock to the rope reel. At the same time, the rotational force of the rope reel is accumulated in the damper spring as a result of the twisting of the damper spring. When the rotational force of the rope reel exceeds the starting resistance of the engine, the rotational force accumulated in the damper spring is released to rotate the cam, whereby the engine is started.
In a recoil starter in which a torsion coil-like damper spring is placed between a rope reel and a cam as described above, in the case where an engine has a large starting resistance, a phenomenon occurs that, when the damper spring is twisted to accumulate the rotational force, the damper spring is tightly wound around outer peripheral faces of the rope reel and the cam. In the conventional art described above, the damper spring is formed into a torsion coil spring-like shape in which a steel wire member having a circular section shape is spirally wound in a plurality of turns. The damper spring is strongly tightly wound around outer peripheral faces of bosses formed on the rope reel and the cam, and the wire member of the damper spring having a circular section shape enters between joining faces of the bosses of the rope reel and the cam. Therefore, the cam is pressed in the axial direction to increase the rotational resistance, or a part of the damper spring is irregularly deformed, so that the durability of the damper spring is impaired.
Components such as the rope reel and the cam are often made of a plastic material in order to reduce the weight. When the damper spring having a circular section shape is strongly tightly wound around outer peripheral faces of such components, therefore, the outer peripheral faces of the components are deformed because the contact areas between the spring and the components are narrow, thereby causing another problem in that the durabilities of the components are impaired. In order to enhance the capacity for accumulating a rotational force in the damper spring so as to enable the engine to be easily started, the diameter of the wire member constituting the damper spring may be enlarged, and the number of turns may be increased. However, this countermeasure involves a problem in that the total length of the damper spring is prolonged, and the size of the recoil starter is increased, with the result that it is impossible to miniaturize the recoil starter.